hypo (Official Hive Approximator)
07-24-02 06:03
No 336535
      grey CuSO4 ???  Bookmark   

the goal of the exercise was to dry acetone.

old, blue CuSO4 was placed in a flask an heated to 200-250C. strangely the
powder did not become white like maybe two years ago, but grey!

acetone was added and the thing stirred with moisture protection for some hours.
the undissolved powder did not become noticeably more blue. acetone was distilled
off and in order to test the CuSO4, water was added to the residue. result: a _green_
solution (!?!?). only after multiple decanting and refilling with water
did the water finally get a blue colour!

any explanations???
 
 
 
 
    demorol
(Hive Bee)
07-24-02 12:17
No 336631
      I think all the water wasn't evaporated so the ...  Bookmark   

I think all the water wasn't evaporated so the crystals turned grey instead of white. Next time try to heat them a little bit longer. Or maybe the sulfate isn't good anymore. But if you dried the acetone sucessfully you shouldn't be worried.

Life without chemistry would be a mistake.
 
 
 
 
    hypo
(Official Hive Approximator)
07-25-02 00:50
No 336874
      hmmm...  Bookmark   

> I think all the water wasn't evaporated so the crystals turned grey instead of white.

the trial was repeated, this time using the gas stove
on full blast --> same result. looking closely it looks
like the CuSO4 turns first white then grey (pretty dark
grey even).

> But if you dried the acetone sucessfully you shouldn't be worried.

well, but that's the problem! how to know if it was dried?
the grey powder did not become much more blue!
 
 
 
 
    raffike
(Hive Bee)
07-25-02 05:36
No 336920
      Maybe your ace was already dry.  Bookmark   

Maybe your ace was already dry.Check if your CuSO4 dissolves in water giving blue solution.If so then it should be CuSO4.Or spray some of your CuSO4 with water and it should turn light-blue.

A friend with speed is a friend indeed
 
 
 
 
    Rhodium
(Chief Bee)
07-25-02 11:56
No 337007
      Is it theoretically possible that some CuSO4 ...  Bookmark   

Is it theoretically possible that some CuSO4 decomposed to another Cu salt?
 
 
 
 
    foxy2
(Distinctive Doe)
08-09-02 00:11
No 343405
      Maybee  Bookmark   

Probably into a tiny bit of CuO.
CuO is BLACK, so a tiny amount of it could easily turn a white powder grey.  Thats my guess.

I doubt you have anything to worry about.

Those who give up essential liberties for temporary safety deserve neither liberty nor safety
 
 
 
 
    Kinetic
(Newbee)
08-09-02 04:22
No 343445
      a little of topic  Bookmark   

From 'Advanced Practical Organic Chemistry' (like an advanced version of Zubrick), the best thing to dry acetone with is 3A molecular sieves. It lists about 20 solvents, and gives preliminary and rigorous drying conditions for each. If anyone is interested I'll start a new thread on this, because it has been very useful to me so far.
 
 
 
 
    Chromic
(Synaptic Self-Mutilator)
08-09-02 08:40
No 343504
      Doubt it  Bookmark   

I doubt the CuSO4 lost the SO3 and became CuO. Likely hypo just got it fully anhydrous.

My CuSO4 looks light green/blue when mostly dry, but light grey when totally dry. The Merck seems to agree saying that "CuSO4 is grayish-white to greenish-white rhombic crystals or amorphous powder". And that on heating it decomposes above 560, a temperature unobtainable in glassware.